New Diff 3.91 OPEN - Now the fun begins!

[leicesterboy15]

Why is a 735i diff different to a 535i diff? Will a 740i diff be different to a 540i diff? Is the 3.64 LSD diff a worthwhile upgrade to my 540i auto? I thought the LSD diff was the best? Questions questions......sounds like you're having fun anyway!

[e34.535i.sport]

Why is a 735i diff different to a 535i diff? Will a 740i diff be different to a 540i diff? Is the 3.64 LSD diff a worthwhile upgrade to my 540i auto? I thought the LSD diff was the best? Questions questions......sounds like you're having fun anyway!

Hey man long time no speaky! Err... I've no idea why it's different, but I done some research on realoem and there seems to be two versions of the seals I bought and murphys law ensured they give me the wrong one! AND they have to be ordered from Z Germany...

The only differences between diffs generally from my research seems to be case size (540i's/M5's have large case, 535i/530i/525i have medium case)... I think you can make smaller case diff works in bigger frame cars if you really want to. Input/output flanges can also differ, enough I think mine are the same so don't have to mess with them!

LSD is preferred for fast cornering and reduced wheelspin as far as I'm aware, whereas I'm more of a 'nifty off the line' kinda guy and I'm not adverse to the odd chirp of the enduros from time to time LOL!

Looking at this http://www.bmwe34.net/E34main/Upgrade/Recipe.htm , I think a 3.64 would be quite a big jump up and might make your gears quite short?! A 3.15, 3.23 or 3.46 might suit your car but I suppose it depends on your driving style?! I don't mind shortening up the gears a little in order to gain acceleration personally... This may also be of some use to you incase you haven't seen it before: http://www.vinesauto.com/diffratio.htm

Seems like the 3.15 out of a 750il *should* swap into yours easy enough... Tempted?!

[e34.535i.sport]

Good news! The diff's all cleaned up, new seals/snap rings are in and so is the fluid.

I'll post pic's soon as I get the laptop sorted to import pictures. Now to find the install disc...

[leicesterboy15]

LOL! You have a way with words!

Yes its been a while! I've been loitering but not really had any time to do any work on the car and looking on here gets me frustrated that I don't have time to do any jobs! The list is building up though so I need to put a plan into action (first I need a plan).

hmm...the diff from a 750? Sounds very tempting, thanks for the links - I'll do some reading up first.

Keep us posted on the diff upgrade!

[e34.535i.sport]

SCOUSE diff...

[whiskychaser]

When its installed you may want to show it off:

http://www.oznium.com/forum/topic3633

[e34.535i.sport]

When its installed you may want to show it off:

http://www.oznium.com/forum/topic3633

LOL! Should stick some of them neons on it and be a 'proper' scouser!

[e34.535i.sport]

It's in!!

First impressions...

Took it out for a short test drive (only a few mile) to check all is well and it certainly is! The new 3.91 is quiet and feels really smooth. The revs certainly rise quicker than before, which gives the feeling of effortless acceleration. I'm going to go on a more extensive test drive and report back fully but it certainly feels quicker off the line and at the lower end of each gear. Can't comment on the swap from LSD to open just yet, only time will tell.

I must say thanks a million to my good friend Colin (aka Whiskychaser!) for giving me a hand with the swap, he is a true gentleman! The job went *almost* perfectly too!

I'm going to make a new 'informative' thread about the whole swap from start to finish for anyone who wants to research it in future, as I got a lot of my information from a variety of different sources. I will obviously be able to give details of my personal experience too, which may be useful to someone at some point.

Overall - great job, great result and had a great time doing it. Recommended!

[whiskychaser]

I'm going to make a new 'informative' thread about the whole swap

I'm sure you will include a section on loctite and nuts IIRC it was 1-all on the oops front

[632 Regal]

Glad it worked out pretty smooth. When I swapped to a taller gear in the 530 the mileage went up 2 in the city and stayed the same hwy even though the engine revs a bit higher.